February 2008

Technology leap allows 2,000-kilometer link

In nations like Brazil, China, and India, governments face the challenge of supplying densely populated urban centers with power from remote generating stations in an efficient and environmentally responsible manner. 

According to the American National Standards Institute (ANSI), a new technology known as ultra-high voltage (UHV) offers a viable solution. 

Delivering voltages of 1,000 kilovolt (kV) alternating current or higher and a minimum of 800 kV direct current, UHV technology can carry large quantities of electricity long distances. 

It can do so over a single power line corridor and with minimal loss of power. International standards for this emerging technology have yet to be developed. 

Indeed, ABB has already won orders worth $440 million from the State Grid Corp. of China and other partners to provide new ultrahigh-voltage technology for the world's longest power transmission link. 

The power superhighway running 1,240 miles (2,000 kilometers) from western China to the highly industrialized coastal area in the east will have a capacity of 6,400 megawatts. 

That is enough to meet the needs of about 31 million people in China, based on average consumption per capital. The link from the Xiangjiaba hydropower plant to Shanghai will be complete in 2011.

The ultrahigh-voltage direct current (UHVDC) link comprises two substations and a power transmission system using breakthrough technology to transmit electricity at ultrahigh voltage (800 kilovolts), which will minimize the amount of power lost in transmission. 

Increasing the voltage level of electrical transmission creates considerable advantages for the environment, including lower electricity losses and the use of less land compared to traditional overhead lines. UHVDC is particularly suitable for vast countries like China, where the centers that need power are often located far from power sources. 

Transmission losses will be under 7%, significantly less than the losses from conventional 500-kilovolt (kV) high-voltage direct current (HVDC) transmission schemes. 

The savings from using UHVDC compared with HVDC are equivalent to the annual power consumption of more than 900,000 people in China.

The new technology, using thyristor valves equipped with newly developed 6-in thyristors (power semiconductors) and an advanced control system, allows the biggest capacity and efficiency leap in 20 years. 

The increase became possible following advances in  materials for outdoor insulators and advanced control systems.